It's not a non-statement. Rich Hickey explains it well, readability is not about the subjective factors, it's mostly about the objective ones (how many things are intertwined? the code that you can read & consider in isolation is readable. The code that behaves differently depending on global state, makes implicit assumptions about other parts of the system, etc - is unreadable/less readable - with readability decreasing with number of dependencies).
"to most developers who are most likely to interact with this code over its useful lifetime."
This means accounting for the audience. Something unfamiliar to the average random coder might be very familiar to anyone likely to touch a particular piece of code in a particular organization.
Oh, I completely disagree here. Take obfuscation for example, which you can carry on into things like minimized files in javascript. If you ever try to debug that crap without an original file (which happens far more than one would expect) you learn quickly about readability.
Yes.